There must be an existing solution for this, if not, feel free to steal my problem and launch a startup. I'll be your first customer. I think the solution is just a source code repository, but for slides, not code.
Problem:

• Several people
• Several decks
• Several project/feature schedules

This is resulting in a lot of churn, and error:

Multiple versions of a deck exist because User A will fork a version of the deck from the current draft to make changes to some slides. While forked User B makes changes to the draft version. When User A then merges in their changes - copying in the few slides they changed, one of which over-writes User B's changes.

What I think I want is that individual slides could be tagged with a release date or version release number - e.g. a slide . When a user is checking in a slide, and if other users have checked in changes that are not in that slide, the the user is alerted and needs to merge these changes.
Making this messy is that a change can be small but important minor UI corrections or speaker note changes.

we do have MS Teams in use - I've not looked to see if that can provide a "source slide repository", or if we could leverage it in some way.

Thoughts? Or am I insane? (The latter I also know the answer to is yes)